Face-to-face dies with probe pads for pre-assembly testing

ABSTRACT

In accordance with the disclosure, one or both semiconductor dies in a face-to-face arrangement may include a probe pad layer formed on a face of the die to allow the die to be individually tested prior to assembly of the dies. Thus, faulty dies may be discarded individually so they are not included in a composite semiconductor device, thereby increasing device yields. The probe pad layer also allows dies to be matched so that a composite semiconductor device achieves desired performance, which may further increase device yields. In some embodiments, the probe pads of the probe pad layer formed on the face of the die may be used to individually test the die, and may remain inactive, or inert, during operation of the composite semiconductor device.

BACKGROUND

It is sometimes not possible or practical to form a semiconductor device from one integrated substrate (or semiconductor die) that includes all of the circuitry desired for the device. Thus, semiconductor devices have been formed from two or more semiconductor dies. Forming a semiconductor device from multiple dies may be challenging. For example, there may be hundreds to thousands of connections required to transmit signals between chips. To achieve high speed operation, connection resistance should be low with short path lengths to minimize inductive and capacitive effects. Further, as semiconductor devices scale and more transistors are integrated into a device, the power and current levels required to operate the transistors may also increase—thereby making power delivery more challenging. Additionally, semiconductor device yields may be reduced, as the entire multi-die device may need to be discarded after testing. Other challenges include arranging components of semiconductor dies to avoid interference between the components that may degrade device performance.

Conventionally, a face-to-face arrangement of semiconductor dies is assembled at a fabrication facility to form a semiconductor device. The composite semiconductor device is then provided to a testing facility where it is tested for proper performance. If the semiconductor device fails testing, the entire device is discarded. For example, if either semiconductor die includes a critical fault or the composite semiconductor device does not meet performance requirements the entire device may need to be discarded after testing, thereby reducing semiconductor device yields.

SUMMARY

The present disclosure relates to approaches for enhancing semiconductor arrangements that include face-to-face semiconductor dies. In some respects, one or both of the semiconductor dies may include probe pads formed over the semiconductor substrate of the die to test the semiconductor die prior to mounting the semiconductor dies face-to-face.

Disclosed approaches provide for one or both semiconductor dies in a face-to-face arrangement including a probe pad layer formed on a face of each die to allow the die to be individually tested prior to assembly of the dies. Thus, faulty dies may be discarded individually so they are not included in a composite semiconductor device, thereby increasing device yields. The probe pad layer also allows dies to be matched so that a composite semiconductor device achieves desired performance, which may further increase device yields. In some embodiments, each semiconductor die may be tested (e.g., at a fabrication facility pre-dicing), then additional interface layers (e.g., comprising bump pads and dielectric material) may be formed over the probe pad layer and used to bond the semiconductor dies in a face-to-face arrangement to form a composite semiconductor device. The composite semiconductor device may then be tested using a different probe pad layer. In some embodiments, the probe pads of the probe pad layer formed on the face of the die may be used to individually test the die, and may remain inactive, or inert, during operation of the composite semiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

The present systems and methods for face-to-face dies probe pads for pre-assembly testing is described in detail below with reference to the attached drawing figures, wherein:

FIG. 1A is a diagram of an example cross-section of a face-to-face arrangement of semiconductor dies, in accordance with some embodiments of the present disclosure;

FIG. 1B is a diagram of an example cross-section of a face-to-face arrangement of semiconductor dies, in accordance with some embodiments of the present disclosure;

FIG. 1C is a diagram of an example cross-section of a face-to-face arrangement of semiconductor dies, in accordance with some embodiments of the present disclosure;

FIG. 2 is a diagram of an example cross-section of a semiconductor package that includes a face-to-face arrangement of semiconductor dies, in accordance with some embodiments of the present disclosure;

FIG. 3A is a diagram of an example cross-section of a face-to-face arrangement of semiconductor dies that includes a void for an inductor, in accordance with some embodiments of the present disclosure;

FIG. 3B is a diagram of an example cross-section of a face-to-face arrangement of semiconductor dies that includes a void for an inductor, in accordance with some embodiments of the present disclosure;

FIG. 4A is a diagram of an example cross-section of a semiconductor die including probe pads for testing prior to including the semiconductor die a face-to-face arrangement of semiconductor dies, in accordance with some embodiments of the present disclosure;

FIG. 4B is a diagram of an example cross-section of a semiconductor die including additional interface layers formed over the probe pads of FIG. 4A, in accordance with some embodiments of the present disclosure;

FIG. 4C is a diagram of an example top view of a testing tile structure which may be included in a semiconductor die, in accordance with some embodiments of the present disclosure;

FIG. 4D is a diagram of an example top view of an arrangement of testing tile structures which may be included in a semiconductor die, in accordance with some embodiments of the present disclosure; and

FIG. 5 is a flow diagram showing a method for testing at least one semiconductor die prior to assembly in a face-to-face arrangement with another semiconductor die, in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure relates to approaches for enhancing semiconductor arrangements that include face-to-face semiconductor dies.

The challenges in forming semiconductor devices from multiple dies has impacted the types of devices, configurations, and components found in multi-die devices. Multi-die devices are often provided with dies mounted in a face-to-back arrangement. In particular, single dies are often front to back so a stacked arrangement may naturally follow from this configuration by stacking similarly arranged dies. However, using a face-to-back arrangement may require all signals to be communicated between the dies using Through Silicon Vias (TSVs) that extend through the entire bottom die. The size of the TSVs results in a lower density of interconnects between the dies, thereby limiting performance and design flexibility. Further, the dies may be connected using microbumps that require an underfill that compromises the thermal performance of the composite structure.

A face-to-face arrangement may allow for significantly higher density of interconnects between the dies by forming interconnects from bump pad metal, but is a less natural arrangement and introduces significant challenges from a design and fabrication standpoint. For example, semiconductor devices have not used a face-to-face arrangement of semiconductor dies that each include a graphics processing unit (GPU) due to these challenges. In such configurations, many signals may be needed for the GPUs to communicate between chips, the GPU in a semiconductor die may require more power than can practically be delivered, and die sizes may be large enough that yields are prohibitively low. Further, it may be desirable to form one or more inductors over the semiconductor substrate of one or both dies, such as for high speed clock operation and/or power filtering, but interference from an adjacent die may degrade an inductor's performance. As such, these types of inductors have not been used in semiconductor devices with face-to-face die arrangements.

In contrast to conventional approaches, one or both semiconductor dies in a face-to-face arrangement may include a probe pad layer formed on a face of the die to allow the die to be individually tested prior to assembly of the dies. Thus, faulty dies may be discarded individually so they are not included in a composite semiconductor device, thereby increasing device yields. The probe pad layer also allows dies to be matched so that a composite semiconductor device achieves desired performance, which may further increase device yields. For example, where each die includes a number of processing cores, testing may be used to bypass faulty cores and select dies so that the composite semiconductor device collectively includes a threshold number of active cores. In some embodiments, each semiconductor die may be tested (e.g., at a fabrication facility pre-dicing), then additional interface layers (e.g., comprising bump pads and dielectric material) may be formed over the probe pad layer and used to bond the semiconductor dies in a face-to-face arrangement to form a composite semiconductor device. The composite semiconductor device may then be tested using a different probe pad layer. In some embodiments, the probe pads of the probe pad layer formed on the face of the die may be used to individually test the die, and may remain inactive during operation of the composite semiconductor device.

In further contrast to conventional approaches, disclosed approaches provide for forming an inductor over the semiconductor substrate of one or both dies in a face-to-face die arrangement while reducing the parasitic capacitance between the inductor and the adjacent die. In disclosed embodiments, a semiconductor device may include a void (e.g., an air gap) between the inductor and the adjacent die to reduce the parasitic capacitance between the inductor and the adjacent die. The void may be formed in the die that includes the inductor and/or the adjacent die. In some respects, the void may be etched in interface layers (e.g., comprising bump pads and dielectric material) between the semiconductor dies, and may extend along the length of the inductor.

Also in contrast to conventional approaches, disclosed approaches provide for a TSV of a first semiconductor die that extends from a semiconductor substrate of the first semiconductor die on an insulated path through at least one metallization layer of the die to electrically and mechanically connect to a different metallization layer to supply power to the second semiconductor die. By extending the TSV, resistance at higher layers (layers further from source) may be reduced allowing for enhanced power delivery to the second semiconductor die. Resistance may further be reduced by allowing for the TSV to electrically and mechanically connect to a thicker metallization layer than would otherwise be possible. In an example and non-limiting embodiment, the thicker metallization layer may have a highest thickness of all of the metallization layers (e.g., a topmost or near-topmost metallization layer of a metallization stack). Also, in some embodiments, the metallization layer that the TSV electrically and mechanically connects to is capable of supplying power to both semiconductor dies. The first semiconductor die may be a top die or a bottom die in a face-to-face arrangement. Further, where additional dies are included in a die stack, any number of the dies may include one or more TSVs that extend from a semiconductor substrate of the die on an insulated path through at least one metallization layer of the die to electrically and mechanically connect to a different metallization layer to supply power to another die.

With reference to FIG. 1A, FIG. 1A is a diagram of an example cross-section of a face-to-face arrangement 102 of semiconductor dies, in accordance with some embodiments of the present disclosure. It should be understood that this and other arrangements described herein are set forth only as examples. Other arrangements and elements may be used in addition to or instead of those shown, and some elements may be omitted altogether. Further, the drawings and illustrations in the present application are not necessarily to scale, and do not necessarily indicate actual relative dimensions.

The face-to-face arrangement 102 includes at least a semiconductor die 104 and a semiconductor die 106. The semiconductor die 106 may include a semiconductor substrate 108, a metallization region 110, an interface region 112, and an interface region 114. The semiconductor die 104 may include an interface region 124.

As an overview, the semiconductor die 106 may include any number of Through Silicon Vias (TSVs), such as a TSV 120 and a TSV 122. While the face-to-face arrangement is described with respect to TSVs, such as the TSV 120 and the TSV 122, the TSVs may more generally be referred to as Through Wafer Vias (TWVs) or Through Chip Vias (TCVs), as some embodiments may use a non-silicon material. One or more of the TSVs, such as the TSV 120 may extend from the semiconductor substrate 108 of the semiconductor die 106 through at least one metallization layer of the metallization region 110 to a metallization layer of the metallization region 110 to supply power to the semiconductor die 104 through the metallization layer, the interface region 112 of the semiconductor die 106, and the interface region 124 of the semiconductor die 104. By extending the TSV through at least one metallization layer of the metallization region 110, power distribution to the semiconductor die 104 may be enhanced.

The semiconductor substrate 108 includes semiconductor material, such as single-crystal semiconductor material. In the present example, the semiconductor substrate 108 is a silicon substrate and more particularly is monocrystalline silicon. However, the semiconductor substrate 108 may comprise any suitable semiconductor material(s), such as a group IV semiconductor material or group III-V semiconductor material.

Group IV refers to a semiconductor that includes at least one group IV element such as silicon (Si), germanium (Ge), and carbon (C), and may also include compound semiconductors such as silicon germanium (SiGe) and silicon carbide (SiC), for example. Group IV also refers to semiconductor materials which include more than one layer of group IV elements, or doping of group IV elements to produce strained group IV materials, and may also include group IV based composite substrates such as single-crystal or polycrystalline SiC on silicon, silicon on insulator (SOI), separation by implantation of oxygen (SIMOX) process substrates, and silicon on sapphire (SOS), for example.

Group III-V refers to a compound semiconductor including at least one group III element and at least one group V element. By way of example, a group III-V semiconductor may take the form of a III-Nitride semiconductor. III-Nitride or III-N refers to a compound semiconductor that includes nitrogen and at least one group III element such as aluminum (Al), gallium (Ga), indium (In), and boron (B), and including but not limited to any of its alloys, such as aluminum gallium nitride (AlxGa(1-x)N), indium gallium nitride (InyGa(1-y)N), aluminum indium gallium nitride (AlxInyGa(1-x-y)N), gallium arsenide phosphide nitride (GaAsaPbN(1-a-b)), aluminum indium gallium arsenide phosphide nitride (AlxInyGa(1-x-y)AsaPbN(1-a-b)), for example. III-N also refers generally to any polarity including but not limited to Ga-polar, N-polar, semi-polar, or non-polar crystal orientations. A III-N material may also include either the Wurtzitic, Zincblende, or mixed polytypes, and may include single-crystal, monocrystalline, polycrystalline, or amorphous structures.

One or more electronic circuits may be formed, at least partially within the semiconductor substrate 108. An electronic circuit may include one or more transistors, such as a transistor 126. In the present example, the electronic circuit may form at least a portion of a GPU. For example, the semiconductor die 106 may be a GPU die. However, various types and configurations of electronic circuits are contemplated as being within the score of the present disclosure. As some examples, the semiconductor substrate 108 may include one or more circuit components of a processing unit, a Central Processing Unit (CPU), a single transistor (e.g., a power transistor), a logic circuit, a power circuit, a System on Chip (SoC), and a transmitter and/or receiver. Where the semiconductor substrate 108 includes a processing unit, the processing unit may include any number of cores. For example, where the processing unit is a GPU, the GPU may include multiple Streaming Multiprocessors (SMs) and each Streaming Multiprocessor may include a number cores.

The metallization region 110 may be formed on the semiconductor substrate 108 and comprise any number of metallization layers and interlayer dielectric layers. Of the metallization layers shown in FIG. 1A, a metallization layer 130, a metallization layer 132, and a metallization layer 134 are individually labeled. Also, of the interlayer dielectric layers shown in FIG. 1A, an interlayer dielectric layer 136 and an interlayer dielectric layer 138 are individually labeled. The metallization layers of the metallization region 110 may interconnect the various circuit components and/or electronic circuits of the semiconductor die 106 and/or the semiconductor die 104. The number of the metallization layers included in the metallization region 110 and the thickness of those layers may vary depending on the design of the semiconductor die 106 and the circuit components and electronic circuits included in the semiconductor die 106. Generally, the thickness of the metallization layers may remain constant, or may increase toward a face 140A of the semiconductor die 106 and a face 140B of the semiconductor die 104. As a specific example, the metallization region 110 may include sixteen metallization layers. The bottom six metallization layers (e.g., including the metallization layer 130) may have the same thickness, followed by four metallization layers that are (as a non-limiting example) three to four times thicker than the bottom metallization layers, followed by two metallization layers (e.g., the metallization layers 132 and 134) that are (for example and without limitation) ten times thicker than the bottom metallization layers.

In various examples, different metallization layers may be used for different purposes, which may depend on the thickness of the metallization layers. The density of routing which may be implemented using a metallization layer may decrease as the thickness of a metallization layer increases. However, the resistivity of a metallization layer may also decrease as the thickness of a metallization layer increases. Thus, in some examples, thicker metallization layers, such as the metallization layers 132 and 134 may be configured for power distribution and/or global clock distribution. Thinner metallization layers, such as the metallization layer 130 may be configured for local signal routing, such as to connect local transistors (e.g., to the transistor 126). Other metallization layers (e.g., with a thickness between the metallization layer 130 and the metallization layers 132 and 134) may be configured for bussing (e.g., between an electronic circuit comprising the transistor 126 and an electronic circuit comprising a transistor 142), lower level clock distribution, and/or power routing.

Face-to-Face Dies with Enhanced Power Delivery Using TSVs

As described herein, one or more TSVs, such as the TSV 122 and/or the TSV 120 may extend from the semiconductor substrate 108 of the semiconductor die 106 on an insulated path through at least one metallization layer of the metallization region 110 to electrically and mechanically connect to a different metallization layer(s) of the metallization region 110 to supply power to the semiconductor die 104, to the different metallization layer(s), and to the components connected to the different metallization layer(s). In the example shown, the TSV 120 extends through the metallization layer 130 and each metallization layer below the metallization layer 132 in the metallization region 110 to contact the metallization layer 132. However, in other examples a TSV may extend through any number of metallization layers to contact any metallization layer of the metallization region 110. For example, where the metallization region 110 includes two metallization layers, the TSV may extend through the bottom metallization layer to contact the top metallization layer. Also, in the example shown, rather than contacting the metallization layer 132, the TSV may contact the metallization layer 134 or any other metallization layer above the metallization layer 130.

By extending the TSV through at least one metallization layer of the metallization region 110, power distribution to the semiconductor die 104 may be enhanced. For example, this may reduce the resistance of the power supply path to the semiconductor die 104, as a TSV typically has low resistance. The power supply path may run from the interface region 114 of the semiconductor die 106 to the TSV 120, through the metallization layer 132 (e.g., a metallization segment 146), through vias in the interlayer dielectric layer 136, through the metallization layer 134 (e.g., a metallization segment 148), and through the interface region 112 to the interface region 124 of the semiconductor die 104. Resistance may further be reduced by allowing for the TSV to connect to a thicker metallization layer than would otherwise be possible. For example, the metallization layer 130 may be the thinnest and most highly resistive of the metallization layers in the metallization region 110, and may be bypassed by extending the TSV 120 through the metallization layer 130.

The number of metallization layers in the metallization region 110 that a TSV is extended through and the thickness of the metallization layer that the TSV contacts may vary depending on the design of the face-to-face arrangement 102 and the circuit components and electronic circuits included in the face-to-face arrangement 102. For example, these factors may vary depending on the routing and layout requirements of the face-to-face arrangement 102, as extending a TSV may introduce routing blockage in the metallization region 110. Also, these factors may vary depending on the power distribution requirements of the face-to-face arrangement 102. In the example shown, the TSV 120 is configured to supply power to circuit components in both the semiconductor die 104 and the semiconductor die 106. For example, from the metallization layer 132, power may be distributed to circuit components such as the transistor(s) 126 through a routing path 144 in the metallization region 110 to reach the semiconductor substrate 108. The routing path 144 includes metallization arranged in a column, but this arrangement may vary.

In the present example, the semiconductor die 104 and the semiconductor die 106 have substantially the same power distribution requirements. For example, the semiconductor die 104 and the semiconductor die 106 may include the same electronic circuitry. Thus, the TSV 120 is configured to deliver substantially the same power to the semiconductor die 104 and the semiconductor die 106. However, the TSV 120 may in other examples be configured to deliver more power to the semiconductor die 104 than the semiconductor die 106 or more power to semiconductor die 106 than the semiconductor die 104. In some embodiments, the TSV 120 may be configured to deliver power to the semiconductor die 104, but not to the semiconductor die 106 or not to a circuit component in the semiconductor substrate 108 of the semiconductor die 106. Also, while the TSV 120 and the TSV 122 both contact the same metallization layer in the example shown, different TSVs within the semiconductor die 106 may extend through a different number of metallization layers to contact different metallization layers.

In various embodiments, the interface region 112 of the semiconductor die 106 may be formed on the metallization region 110 and may electrically and mechanically couple the semiconductor die 106 to the semiconductor die 104. For example, the semiconductor die 104 may be mounted face-to-face with the semiconductor die 106 to form an electrical and mechanical interface 150 at the interface region 112 of the semiconductor die 106 and the interface region 124 of the semiconductor die 104.

Various techniques may be used to form the interface region 112 of the semiconductor die 106 and the interface region 124 of the semiconductor die 104 so as to provide the electrical and mechanical interface 150. The interface region 112 and the interface region 114 may vary depending on various factors, such as the desired characteristics for the electrical and mechanical interface 150. As an example, the interface region 112 and the interface region 114 may use a different technique and/or comprise different materials when only power is to be transferred across the electrical and mechanical interface 150, as opposed to a signal(s) and power. FIG. 1B shows an example of the interface region 112 and the interface region 114 along with an example of the semiconductor die 104.

With reference to FIG. 1B, FIG. 1B is a diagram of an example cross-section of a face-to-face arrangement 102 of semiconductor dies, in accordance with some embodiments of the present disclosure. In the example of FIG. 1B, the interface region 112 and the interface region 114 each include bonding dielectric (e.g., bonding oxide) and inter-die interface pads (e.g., formed from one or more bump pad layers and/or inter-die interface pad layers) that forms the electrical and mechanical interface 150. By way of example, the bonding dielectric may include a bonding dielectric layer 152 (e.g., a bonding oxide layer). Also by way of example, inter-die interface pads may include bump pads in the bonding dielectric layer 152, of which bump pads 154, 156, and 158 are individually labeled. The bump pads 154 and 156 may be used to supply power to the semiconductor die 104 and the interface region 112. Bump pad vias, such as a bump pad via 160, may be used to connect the bump pads 154 and 156 to the metallization layer 134. The bump pad 158 may, for example, be used to communicate a signal between the semiconductor die 104 and the semiconductor die 106. Any number of bump pads may be used to facilitate the exchange of power and/or signals between the semiconductor die 104 and the semiconductor die 106.

The interface region 124 of the semiconductor die 104 may be similar to the interface region 112 of the semiconductor die 106, with similarly depicted elements representing corresponding features in the interface region 112. However, in other examples, the interface region 124 may include different elements than the interface region 112. As indicated in FIG. 1B, the interface region 124 of the semiconductor die 104 may receive power from the TSV 120, which may be delivered to an electrical circuit(s) comprising one or more circuit components, such as a transistor 162 formed at least partially in a semiconductor substrate 164 of the semiconductor die 104 (e.g., using one more metallization layers in a metallization region 166).

The description of the semiconductor substrate 108 and the semiconductor die 106 may apply to the semiconductor substrate 164 and the semiconductor die 104 and is therefore not repeated. However, the examples may be mixed and matched such that the semiconductor substrate 108 may comprise similar or different material than the semiconductor substrate 164. Similarly, the description of the metallization region 110 and the semiconductor die 106 may apply to metallization region 166 and the semiconductor die 104 and is therefore not repeated (e.g., the same or a different number of layers may be included of similar or different thicknesses). However, in some embodiments the semiconductor die 104 does not include the metallization layers 166 and/or may include a single metallization layer.

In the example of FIG. 1B, the semiconductor die 106 and the semiconductor die 104 may be fabricated using the same mask set and the same base wafer material. This allows for reduced cost by avoiding an additional mask set. Further, device yields may be increased, for example, as fabrication can be tailored to a single design.

As an example of fabricating the face-to-face arrangement 102, a wafer comprising the semiconductor substrate 108 may be processed to fabricate the semiconductor die 106 comprising the metallization region 110. The interface region 112 may be formed on the metallization region 110 and the wafer may be diced, or singulated, to form individual dies including the semiconductor die 106.

Also, a different wafer comprising the semiconductor substrate 164 may be processed to fabricate the semiconductor die 104 comprising the metallization region 166. This processing may use the same mask set used for the semiconductor die 106 (or a different mask set in some embodiments). The interface region 124 may be formed on the metallization region 166. This processing may use the same mask set as used for the interface region 112 of the semiconductor die 106, or a different mask set. A pick and place machine may be used to mount the singulated dies formed from the semiconductor substrate 108 with the respective unsingulated dies formed from the semiconductor substrate 164 in face-to-face arrangements. This may form the face-to-face arrangement 102. The singulated dies may then be thinned and the TSVs, such as the TSV 120 and the TSV 122 may be revealed. Subsequently, the interface region 114 may be formed and the face-to-face arrangements may be singulated.

In some embodiments, the semiconductor die 104 is bilaterally symmetrical to the semiconductor die 106 (and/or the mask set(s) used to form the semiconductor dies 104 and 106), as indicated by symmetry line 170. When mounting the semiconductor die 106 and the semiconductor die 106 in the face-to-face arrangement 102, the semiconductor die 106 may be rotated and flipped around the symmetry line 170 (like book pages) to align symmetrically-positioned contact points on the interface regions 112 and 124. Other types of symmetry are covered by the disclosure, such as quadrilateral symmetry and/or rotational symmetry. For example, the semiconductor die 106 may be rotated 180 degrees and flipped around the symmetry line 170 to align symmetrical contact points on the interface regions 112 and 124.

Where the semiconductor dies (and/or masks and/or surface contacts on the face of the dies) are symmetrical, in some embodiments, one or more structures in the semiconductor die 106 may have a corresponding structure in the semiconductor die 104 that is configured for a different purpose or function than in the semiconductor die 106. For example, FIG. 1B shows a structure 176 (an electrically conductive structure) of the semiconductor die 106 (including at least the TSVs 120 and 122, connected metallization segments, such as the metallization segments 146 and 148, and connected microvias, such as those of the routing path 144), which may correspond to a structure 178 of the semiconductor die 104. In the semiconductor die 106, the structure 176 may be configured to supply power to the semiconductor die 104. In some embodiments, the structure 176 for purposes of this description does not refer to connected components (e.g., the bump pad via 160 and the bump pads 154 and 156) in the interface region 112, while in others it may. For example, the interface region 124 and the interface region 112 may not include analogous and/or duplicate structure. In the semiconductor die 104, the structure 178 may be configured to supply power to an electronic circuit in the semiconductor substrate 164 (e.g., using bump pad vias in the interface region 112, such as the bump pad via 160 and bump pads, such as the bump pads 154 and 156), may remain unused or inactive (e.g., electrically inert) as a vestigial structure (e.g., not used to carry signals and/or power), or may be configured to perform a different function, such as to supply power to a semiconductor die (e.g., via one or more portions of the structure 178 that correspond to the TSVs 120 and/or 122) and/or electrical component on the semiconductor die 104 (e.g., via the interface region 124 which may be configured similar to or different than the interface region 112 with respect to bump pad vias and bump pads) in embodiments that include those additional elements.

FIG. 1B also shows a structure 182 (e.g. including connected metallization segments and microvias) of the semiconductor die 104, which may correspond to a structure 184 of the semiconductor die 106. Similar to the structures 176 and 178, the structures 182 and 184 may be an example of one or more corresponding structures that are configured for a different purpose or function for the semiconductor dies 104 and 106. Also similar to the structures 176 and 178, in some embodiments, the structures 182 and 184 for purposes of this description do not refer to connected components (e.g., bump pad vias and bump pads in the interface regions 112 and 124, while in others they may. As indicated by the region 172, the structures 178 and 182 may be configured to connect and/or align across the semiconductor dies 104 and 106. A similar configuration is shown for a region 174. In some embodiments, such regions may be vestigial and may not be used for characterization of the face-to-face arrangement 102.

While the structure 176 and the structure 178 are substantially similar in FIG. 1B, the corresponding structures may be different from one another. For example, even where the same masks are used to form the structures in the semiconductor dies 104 and 106, the corresponding structures may be different. As an example, TSVs may not be formed in the semiconductor die 104, the region 172, and/or the region 174. Referring now to FIG. 1C, FIG. 1C is a diagram of an example cross-section of a face-to-face arrangement 102 of semiconductor dies, in accordance with some embodiments of the present disclosure. In this example, TSVs are not formed in the semiconductor die 104. Thus, the structure 178 may not include TSVs that correspond to the TSVs 120 and 122 of the structure 176, but may otherwise be similar. Additionally or alternatively, as described, portions of the structure 178 in the interface region 124 may be different than portions of the structure 176 in the interface region 112 (or no portion of the structure 178 may be in the interface region 124).

FIG. 1B also shows an example of the interface region 114 of the semiconductor die 106. In the example of FIG. 1B, the interface region 114 includes microbumps, such as a microbump 190A and a microbump 190B, which may serve as power and/or Input/Output (IO) terminals of the face-to-face arrangement 102. Thus, the interface region 114 may comprise a communications and/or power interface to the face-to-face arrangement 102. For example, the microbump 190A and the microbump 190B may be configured as power supply terminals of the face-to-face arrangement 102. The interface region 114 may further include one or more backside redistribution layers, such as a backside redistribution layer 194. The interface region 114 may vary depending on such factors as the packaging used to house the face-to-face arrangement 102, fabrication constraints or technologies, whether the semiconductor die 104 or the semiconductor die 104 is the top die or the bottom die in the face-to-face arrangement 102, and/or whether there are additional semiconductor dies (e.g., in a face-to-face arrangement) and/or electrical components stacked on the face-to-face arrangement 102, etc.

Now referring to FIG. 2, FIG. 2 is a diagram of an example cross-section of a semiconductor package 200 that includes a face-to-face arrangement 102 of semiconductor dies, in accordance with some embodiments of the present disclosure. In the semiconductor package 200, the face-to-face arrangement 102 is electrically and mechanically coupled to an interposer 202 by microbumps 290, which may include the microbumps 190A and 190B of FIG. 1B. The interposer 202 may be electrically and mechanically coupled to a package substrate 204 by solder bumps 210, which may be C4 bumps. Also, the package substrate 204 includes solder balls 212, which may serve as terminals or pins of the semiconductor package 200. The semiconductor package 200 may include other elements not shown, such as encapsulant and additional dies and/or electrical components. One or more of the solder balls 212 may be a package power supply terminal of the semiconductor package 200, and may be electrically connected to the interface region 114 of the semiconductor die 106, such as by the microbump 190A and the microbump 190B. One or more of the solder balls 212 may also be a package signal, or IO terminal of the semiconductor package 200, and may be electrically connected to the interface region 114 of the semiconductor die 106, such as by one or more of the microbumps 290. The semiconductor package 200 is provided as one suitable example of a semiconductor package, but other packaging types and technologies may be used in disclosed embodiments.

Face-to-Face Dies with a Void for Enhanced Inductor Performance

Aspects of the disclosed approaches provide for forming an inductor over a semiconductor substrate of one or both dies in a face-to-face die arrangement while reducing the parasitic capacitance between the inductor and the adjacent die. In disclosed embodiments, the semiconductor device may include a void (e.g., an air gap) between the inductor and the adjacent die to reduce the parasitic capacitance between the inductor and the adjacent die. The void may be etched in interface layers (e.g., comprising inter-die interface pads and dielectric material) between the semiconductor dies, and may extend along the length of the inductor. FIG. 3A shows one such example of a suitable face-to-face arrangement of semiconductor dies, but many different variations are within the score of the present disclosure.

Now referring to FIG. 3A, FIG. 3A is a diagram of an example cross-section of a face-to-face arrangement 302 of semiconductor dies that includes a void for an inductor, in accordance with some embodiments of the present disclosure.

The face-to-face arrangement 302 may be the same as or different than the face-to-face arrangement 102 of FIGS. 1A and/or 1B. In the face-to-face arrangement 302, one or more inductors may be formed over the semiconductor substrate 108 of the semiconductor die 106. Examples in FIG. 3A include an inductor 304 and an inductor 306. The inductors 304 and 306 may be included in the face-to-face arrangement 302 for, as examples, high speed clock operation and/or power filtering (e.g., of power received from a power supply terminal of the face-to-face arrangement 302). In embodiments where the inductor 304 and/or the inductor 306 are used for clocking, the inductor may connect to phase-locked loop (PLL) circuitry (to generate a clock signal) and may not include a connection to a TSV (or a power supply path) and/or to outside of the semiconductor package 200.

In the example shown, the inductors 304 and 306 are formed in the interface region 112. In other examples, one or more inductors may in addition or intead be formed in a different region, such as the metallization region 110. As shown, the face-to-face arrangement 302 includes a void 308 between the inductor 304 and the semiconductor die 104 and a void 310 between the inductor 306 and the semiconductor die 104. The voids 308 and 310 may be an air gap configured to reduce the parasitic capacitance between the inductors 304 and 306 and the semiconductor die 104. The voids 308 and 310 may extend along the length of the inductors 304 and 306 respectively along a direction parallel to the face 140A of the semiconductor die 106. The voids 308 and 310 may also extend from a distal plane on the face 140A of the semiconductor die 106 to the inductors 304 and 306 respectively. For example, the voids 308 and 310 may be formed in the surface of the interface region 112 by etching the voids 308 and 310 in the bonding dielectric layer 152. In other examples, the voids may be etched in additional or different portions of the interface region 112. Also in some embodiments, the voids 308 and 310 may be formed at least partially on the semiconductor die 104. In some examples, the inductor 304 or 306 is at least partially on a distal plane on the face 140A of the semiconductor die 106, and the void 308 or 310 is formed on a distal plane on the face 140B of the semiconductor die 104 rather than on the semiconductor die 106 (e.g., by etching the void(s) in the interface region 124).

The semiconductor die 106 may also include a voided region between the inductor and the backside of the semiconductor die 106 to avoid parasitic capacitance between the inductor and elements of the semiconductor die 106. For example, a voided region 312 is shown, which may extend to the backside of the semiconductor die 106. The voided region 312 may also extend along the length of the inductor 304, similar to the void 308. The voided region 312 is configured to be floating. Thus, while conductive material, such as metallization may be in the voided region 312 (e.g., as fill material to satisfy design rules), the conductive material is floating (e.g., comprising non-signal carrying layers) so as to avoid parasitic capacitance with the inductor 304. FIG. 3B is used to describe additional examples of the face-to-face arrangement 302.

FIG. 3B is a diagram of an example cross-section of the face-to-face arrangement 302 of semiconductor dies that includes a void for an inductor, in accordance with some embodiments of the present disclosure. As shown in FIG. 3B, the semiconductor die 104 may also include a voided region 314 for the inductor 304, which may be similar to the voided region 312. FIG. 3B also shows an example where the semiconductor die 104 includes an inductor 316, a void 318, and a voided region 320, which may be similar to or different than the inductor 304, the void 308, and the voided region 312, respectively. Further, the semiconductor die 106 includes a voided region 322, which may be similar to the voided region 314. Thus, one or both of the semiconductor dies 104 or 106 may include an inductor and corresponding void. Further, the inductor and void may be formed in different layers in each semiconductor die. Also, in various embodiments, an inductor (e.g., the inductor 304, 306, and/or 316) may optionally be formed in one semiconductor die and connected to electronic circuity (e.g., to provide a clock, etc.) in the other die in addition to or instead of the semiconductor die. While like FIG. 3B, FIG. 1B shows the inductors and voids, the face-to-face arrangement 102 may be provided without one or more of those elements. Also, while like FIG. 1B, FIG. 3B shows TSVs that extend through at least one metallization layer, the face-to-face arrangement 302 may be provided without one or more of those elements.

Face-to-Face Dies with Probe Pads for Pre-Assembly Testing

Aspects of the disclosed approaches provide for one or both semiconductor dies in a face-to-face arrangement including at least one probe pad layer formed on a face of the die to allow the die to be individually tested prior to assembly of the dies. Thus, faulty dies may be discarded individually so they are not included in a composite semiconductor device, or dies may be better matched, thereby increasing device yields. In some embodiments, a semiconductor die may be tested (e.g., at a fabrication facility pre-dicing), then additional interface layers (e.g., comprising inter-die interface pads and dielectric material) may be formed over the probe pad layer and used to bond the semiconductor dies in a face-to-face arrangement to form a composite semiconductor device. FIGS. 4A and 4B show one such example used to describe testing, then forming additional interface layers over a semiconductor die prior to including the semiconductor die a face-to-face arrangement of semiconductor dies, but many different variations are within the score of the present disclosure.

FIG. 4A is a diagram of an example cross-section of the semiconductor die 106 including probe pads for testing prior to including the semiconductor die 106 in the face-to-face arrangement 102 of semiconductor dies, in accordance with some embodiments of the present disclosure. The semiconductor die 106 of FIGS. 4A and 4B may correspond to the semiconductor die 106 during fabrication and pre-assembly into the face-to-face arrangement 102.

The interface region 112 of FIG. 4A is formed on a die region 410 on the face 140B of the semiconductor die 106. The die region 410 is shown generically to indicate the broad applicability of the approaches described with respect to FIGS. 4A and 4B, but may in some embodiments include the metallization region 110 and the semiconductor substrate 108. In some embodiments, the interface region 114 is not yet formed on the semiconductor die 106.

The interface region 112 of FIG. 4A includes a plurality of probe pads, of which probe pads 406 and 408 are shown. The probe pads may comprise, for example, aluminum probe pads formed from a probe pad layer(s). In embodiments where the interface region 112 includes at least one inductor, such as the inductor 304 or the inductor 306, one or more of the inductors may also be formed from the probe pad layer(s), as shown, and/or from a different layer(s). The probe pads may be configured to test one or more electronic circuits in the semiconductor die 106, such as an electronic circuit comprising the transistor 126 and/or 142. For example, the probe pads may be electrically connected to the electronic circuit(s) by the metallization region 110 for testing. As an example, the semiconductor die 106 may be tested prior to dicing, along with other similar semiconductor dies on the wafer. Further, this testing may occur at the fabrication facility used to fabricate the wafer.

Subsequent to testing the wafer comprising the semiconductor die 106, the wafer may undergo further processing (e.g., at the fabrication facility) to produce the semiconductor die 106 of FIG. 4B. FIG. 4B is a diagram of an example cross-section of the semiconductor die 106 including additional interface layers formed over the probe pads of FIG. 4A, in accordance with some embodiments of the present disclosure. The additional processing may include forming one or more bonding dielectric layers, such as the bonding dielectric layer 152 over the probe pad layer and/or probe pads. Additionally, any number of inter-die interface pads, such as the bump pads 154, 156, or 158 may be formed in the bonding dielectric layer 152. Further, in embodiments that include one or more inductors, voids—such as the voids 308 or 310—may be formed in the bonding dielectric layer 152. The semiconductor die 106 may then be mounted to the semiconductor die 104 in the face-to-face arrangement 102 using the bonding dielectric layer 152.

In the face-to-face arrangement 102, the probe pads of the probe pad layer may be insulated from the semiconductor die 104 and may remain inactive during operation of the semiconductor die 106. Thus, the probe pads may only be operated for testing of the semiconductor die 106 pre-assembly, but may remain as vestiges and electrically inert in the face-to-face arrangement 102. In other examples, the probe pads may be configured or reconfigured for operation of the semiconductor die 106 and/or the semiconductor die 104 in the face-to-face arrangement 102.

While FIGS. 4A and 4B are described with respect to the semiconductor die 106, FIGS. 4A and 4B may also apply to the semiconductor die 104. For example, the interface region 124 of the semiconductor die 104 may be formed similar to the interface region 112, including testing the semiconductor die 104 at the fabrication facility, then performing additional processing to arrive at the configuration of FIG. 4B. However, in some embodiments the semiconductor die 104 may include probe pads in the interface region 124 while the semiconductor die 106 does not include probe pads in the interface region 112, or the semiconductor die 106 may include probe pads in the interface region 112 while the semiconductor die 104 does not include probe pads in the interface region 124.

To form the face-to-face arrangement 102, the wafer comprising the semiconductor die 106 may be singulated and a pick and place machine may be used to mount the singulated dies formed from the semiconductor substrate 108 with the respective unsingulated dies formed from the semiconductor substrate 164 in face-to-face arrangements including the face-to-face arrangement 102. In embodiments where the semiconductor substrate includes TSVs, the singulated dies may then be thinned and the TSVs, such as the TSV 120 and the TSV 122 may be revealed. Subsequently, the interface region 114 may be formed and the face-to-face arrangements may be singulated. The interface region 114 may be used to test the semiconductor die 104 and/or the semiconductor die 106, such as by testing a composite semiconductor device (e.g., a composite logic circuit) formed from the semiconductor die 104 and the semiconductor die 106 (e.g., in the semiconductor package 200 and/or prior to inclusion in a semiconductor package). This testing may occur at a testing facility separate from the fabrication facility and may use microbumps in the interface region 114, such as the microbump 190A and/or the microbump 190B (e.g. power and signal terminals used during regular operation) and/or may use backside probe pads in the interface region 114, such as a probe pad 192A and/or a probe pad 192B formed in a backside probe pad layer (e.g. prior to formation of the microbumps). As the semiconductor dies may be tested pre-assembly, faulty dies may be discarded so they are not included in a face-to-face arrangement and/or dies may be matched, thereby increasing device yields.

Referring now to FIG. 4C, FIG. 4C is a diagram of an example top view of a testing tile structure 416 which may be included in semiconductor die 106, in accordance with some embodiments of the present disclosure. The semiconductor die 106 may include any number of testing tile structures, which may appear similar to the testing tile structure 416 and may be arranged in a grid-like arrangement. The testing tile structure 416 includes the probe pads 406 and 408, as well as a probe pad 418 and a probe pad 420. In other embodiments the testing tile structure 416 may include a different number of probe pads. During testing, pins of testing hardware may electrically and mechanically interface with the testing tile structure 416 at the probe pads. As an example, the probe pads may each be approximately 50×50 microns, and larger than the inter-die interface pads (e.g., the bump pads 154, 156, and 158).

The probe pad 406 may be configured as a power supply terminal of the testing tile structure 416 and the probe pad 408 may be configured as a ground pad of the testing tile structure 416 during the testing. Further, the probe pads 418 and 420 may be configured as respective signal terminals of the testing tile structure 416 during the testing. While the testing tile structure 416 includes two signal terminals in the example shown, the testing tile structure 416 may be used to test more than two signals in the semiconductor die 106 by serializing the signals. Each probe pad may be electrically connected to a respective portion of a redistribution layer, as shown in FIG. 4C. In the example shown, the portions of the redistribution layer include interdigitated fingers, or rows. Each node on a finger may be coupled to an underlying via and routed to a corresponding circuit element(s) in the semiconductor substrate 108 (e.g., the transistor 126). While the testing tile structure 416 is shown, embodiments of the present disclosure may not use a testing tile structure for testing. Also, the semiconductor die 104 may include a similar or different testing structure.

Referring now to FIG. 4D, FIG. 4D is a diagram of an example top view of an arrangement 430 of testing tile structures 416 which may be included in the semiconductor die 106, in accordance with some embodiments of the present disclosure. While only eight testing tile structures 416 are shown in FIG. 4D, the semiconductor die 106 may include, as an example, thousands of testing tile structures 416. In a specific and non-limiting example, the semiconductor die 106 may by approximately 20 millimeters by 20 millimeters and a testing tile structure 416 may be approximately 200 micrometers by 200 micrometers. Thus, as many as 10,000 testing tile structures 416 may fit in the arrangement 430. However, in the present example, the region 432 does not include a testing tile structure 416. Instead, the region 432 may include one or more other testing tile structures and/or testing structures, or may not include any probe pads or testing structures. In some examples, the region 432 corresponds to a crossbar configured for inter-die communication of signals between the semiconductor die 104 and the semiconductor die 106 in the face-to-face arrangement 102. The crossbar may be used to communicatively couple a processing unit in the semiconductor die 104 with a processing unit in the semiconductor die 106.

Although FIGS. 4C and 4D are described with respect to the semiconductor die 106, FIGS. 4C and 4D may also apply to the semiconductor die 104. For example, the semiconductor die 104 may include similar or different testing structures (e.g., tiles) as the semiconductor die 104 in a similar or different arrangement.

In embodiments where the semiconductor die 106 comprises a processing unit, the testing tile structures 416 may each correspond to one or more respective processing cores of the processing unit (e.g., that underlines the testing tile structure 416). Using the testing tile structures 416, each processing core(s) may be individually tested. For example, where the semiconductor die 106 comprises a GPU, each testing tile structure 416 may correspond to a respective SM and may be used to test the SM. The semiconductor die 106 may be configured (e.g., by the testing hardware) to bypass faulty cores and/or SMs based on the testing the semiconductor die 106. Further, the semiconductor die 106 may be matched to another component for inclusion in a face-to-face arrangement based on the testing of the semiconductor die 106. For example, the semiconductor die 106 and the semiconductor die 104 may each be tested and selected for inclusion in the face-to-face arrangement 102 based on the number of cores and/or SMs that pass the testing (and/or other performance characteristics identified by the testing). This may be done so that the composite semiconductor device collectively includes a threshold number of active cores or otherwise satisfies predetermined performance criteria.

Now referring to FIG. 5, FIG. 5 is a flow diagram showing a method 500 for testing at least one semiconductor die prior to assembly in a face-to-face arrangement with another semiconductor die, in accordance with some embodiments of the present disclosure. The method 500 is described using the semiconductor die 104 and the semiconductor die 106, by way of example only. Further, while the method 500 is described with the semiconductor die 106 being tested, an instance of the method 500 may additionally or alternatively be used with the semiconductor die 104 being tested in place of the semiconductor die 106.

The method 500, at block B502, includes testing a first semiconductor die using probe pads formed on a face of the first semiconductor die. For example, testing equipment may test the semiconductor die 106 by probing the probe pads 406 and 408 of FIGS. 4A. In embodiments where the semiconductor die 106 includes the testing tile structure 416 of FIG. 4C, the probe pads 418 and 420 may also be probed to test the semiconductor die 106.

The method 500, at block B504, includes forming at least an interface layer of the first semiconductor die over the probe pads. For example, after testing the semiconductor die 106, additional interface layers of the interface region 112 may be formed over the probe pads 406 and 408 to result in FIG. 4B. As shown, the interface layers may include the bonding dielectric layer 152 and an inter-die interface pad layer(s) used to form inter-die interface pads such as the bump pads 154, 156, and 158.

The method 500, at block B506, includes mounting the first semiconductor die face-to-face with a second semiconductor die using the interface layer to couple at least one inter- die interface pad of the first semiconductor die to at least one inter-die interface pad of a second semiconductor die. For example, a pick and place machine may be used to mount the semiconductor die 106 to the semiconductor die 106 using the bonding dielectric layer 152 to couple the bump pads 154, 156, and 158 to corresponding bump pads of the semiconductor die 104, as in FIGS. 1B and 3B. In other examples, the bonding dielectric layer 152 may not be used, such as where the inter-die interface pad layer is sufficient (e.g., the top surface of the semiconductor die 106 may be a single inter-die interface pad). As described herein, the semiconductor die 106 and the semiconductor die 104 may form at least part of a composite semiconductor device, which may be tested through the backside of the semiconductor die 106, the semiconductor die 104 (in embodiments where probe pads are included on the backside of the semiconductor die 104), and/or other semiconductor dies which may be in a stack with those semiconductor dies.

Thus, various approaches for enhancing semiconductor arrangements that include face-to-face semiconductor dies have been provided herein. These approaches may be mixed and matched in any suitable combination in order to achieve semiconductor devices with desired characteristics.

As used herein, a recitation of “and/or” with respect to two or more elements should be interpreted to mean only one element, or a combination of elements. For example, “element A, element B, and/or element C” may include only element A, only element B, only element C, element A and element B, element A and element C, element B and element C, or elements A, B, and C. In addition, “at least one of element A or element B” may include at least one of element A, at least one of element B, or at least one of element A and at least one of element B.

The subject matter of the present disclosure is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this disclosure. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the terms “step” and/or “block” may be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly described. 

1. A semiconductor device comprising: a first semiconductor die having, a semiconductor substrate, a logic circuit, a probe pad layer, metallization layers, an inter-die interface pad layer, and a backside interface layer; and a second semiconductor die having a semiconductor substrate; wherein the first semiconductor die is mounted in a face-to-face arrangement with the second semiconductor die; wherein the semiconductor substrate of the first semiconductor die comprises the logic circuit; wherein the backside interface layer of the first semiconductor die is providing a communications interface to the first semiconductor die and the second semiconductor die; wherein the probe pad layer of the first semiconductor die is between the semiconductor substrate of the second semiconductor die and the semiconductor substrate of the first semiconductor die to test the logic circuit through the metallization layers of the first semiconductor die prior to forming the face-to-face arrangement; and wherein the inter-die interface pad layer is formed over the probe pad layer and is communicatively coupling the first semiconductor die and the second semiconductor die.
 2. The semiconductor device of claim 1, further comprising a probe pad layer of the second semiconductor die disposed between the semiconductor substrate of the first semiconductor die and the semiconductor substrate of the second semiconductor die to test a logic circuit in the semiconductor substrate of the second semiconductor die through metallization layers of the second semiconductor die prior to forming the face-to-face arrangement.
 3. The semiconductor device of claim 1, wherein the probe pad layer is part of a plurality of testing tile structures in a grid-like arrangement over the semiconductor substrate of the first semiconductor die.
 4. The semiconductor device of claim 1, wherein the probe pad layer includes a power terminal, and ground terminal, and at least one signal terminal.
 5. The semiconductor device of claim 1, wherein the inter-die interface pad layer is a bump pad layer.
 6. The semiconductor device of claim 1, wherein the inter-die interface pad layer is formed in a bonding dielectric layer that mechanically couples the first semiconductor die to the second semiconductor die.
 7. The semiconductor device of claim 1, further comprising a backside probe pad layer of the first semiconductor die to test a composite logic circuit formed from the first semiconductor die and the second semiconductor die in the face-to-face arrangement.
 8. The semiconductor device of claim 1, wherein each probe pad of the probe pad layer is electrically inert in the face-to-face arrangement.
 9. The semiconductor device of claim 1, wherein the probe pad layer is part of a plurality of testing structures and each testing structure is to test a respective set of one or more cores of a processing unit formed in the semiconductor substrate of the first semiconductor die.
 10. A semiconductor device comprising: a first semiconductor die having, a semiconductor substrate, and a backside interface layer; and a second semiconductor die having, a semiconductor substrate, a logic circuit, a plurality of metallization layers, an inter-die interface pad layer, and a probe pad layer; wherein the first semiconductor die is mounted in a face-to-face arrangement with the second semiconductor die; wherein the backside interface layer of the first semiconductor die is providing a communications interface to the first semiconductor die and the second semiconductor die; wherein the semiconductor substrate of the second semiconductor die comprises the logic circuit; wherein the probe pad layer of the second semiconductor die is between the semiconductor substrate of the second semiconductor die and the semiconductor substrate of the first semiconductor die to test the logic circuit through at least one metallization layer of the plurality of metallization layers of the second semiconductor die prior to forming the face-to-face arrangement; and wherein the inter-die interface pad layer is formed over the probe pad layer and is communicatively coupling the first semiconductor die and the second semiconductor die.
 11. The semiconductor device of claim 10, further comprising a probe pad layer of the first semiconductor die disposed between the semiconductor substrate of the first semiconductor die and the semiconductor substrate of the second semiconductor die to test a logic circuit in the semiconductor substrate of the first semiconductor die through at least one metallization layer of the plurality of metallization layers of the first semiconductor die prior to forming the face-to-face arrangement.
 12. The semiconductor device of claim 10, wherein the inter-die interface pad layer is formed in a bonding dielectric layer that mechanically couples the first semiconductor die to the second semiconductor die.
 13. The semiconductor device of claim 10, further comprising a backside probe pad layer of the first semiconductor die, the backside probe pad layer to test a composite logic circuit formed from the first semiconductor die and the second semiconductor die in the face-to-face arrangement.
 14. The semiconductor device of claim 10, wherein each probe pad of the probe pad layer is electrically inert in the face-to-face arrangement.
 15. The semiconductor device of claim 10, wherein the probe pad layer is part of a plurality of testing structures and each testing structure is to test a respective set of one or more cores of a processing unit formed in the semiconductor substrate of the second semiconductor die.
 16. A semiconductor package comprising: a first semiconductor die having, a semiconductor substrate, a processing unit, a probe pad layer, metallization layers, an inter-die interface pad layer, and a backside interface layer; a second semiconductor die having, a semiconductor substrate, and a processing unit; and package signal terminals to provide signals to a composite logic circuit that includes the processing unit in the first semiconductor die and the processing unit in the second semiconductor die; wherein the first semiconductor die is mounted in a face-to-face arrangement with the second semiconductor die; wherein the probe pad layer of the first semiconductor die is between the semiconductor substrate of the first semiconductor die and the semiconductor substrate of the second semiconductor die to test the processing unit in the first semiconductor die prior to forming the face-to-face arrangement; and wherein the inter-die interface pad layer is formed over the probe pad layer of the first semiconductor die and is communicatively coupling the first semiconductor die and the second semiconductor die to form the composite logic circuit.
 17. The semiconductor package of claim 16, further comprising a backside interface layer of the first semiconductor die, the backside interface layer of the first semiconductor die being electrically connected to the package signal terminals to provide the signals to the composite logic circuit.
 18. The semiconductor package of claim 16, further comprising a backside interface layer of the second semiconductor die electrically, the backside interface layer of the second semiconductor die being connected to the package signal terminals to provide the signals to the composite logic circuit.
 19. The semiconductor package of claim 16, wherein the processing unit in the first semiconductor die is a first graphics processing unit (GPU) and the processing unit in the second semiconductor die is a second GPU.
 20. The semiconductor device of claim 16, wherein each probe pad of the probe pad layer is electrically inert in the face-to-face arrangement. 